Conventionally, one method has been known to mount an electronic component on a wiring board to produce a circuit board. According to this method, a bump is provided on an electrode of an electronic component to join the bump with the electrode on the wiring board. For example, a method has been suggested to transfer electrically-conductive adhesive agent onto electric connection contact points (bumps) of a semiconductor chip by the stamping method for example to heat the conductive adhesive agent while pressing the semiconductor chip to a circuit board (e.g., see Patent Publication 1).
On the other hand, an Integrated Circuit Card (IC card) has been widely used in recent years as a card-type recording medium substituting a magnetic card. A method for mounting a bare chip on an IC card board has been suggested according to which a bare chip having a gold bump is flip-chip-mounted via silver paste or an anisotropic conductive film (e.g., see Patent Publication 2). A technique also has been known that a tip end of a protruded electrode (bump) of an electronic component is caused to bite into an electrode of an IC card board for mounting to use thermoplastic resin to seal the electronic component on the board (e.g., see Patent Publication 3).
In the case of Patent Publication 1 however, the smaller size the mounted electronic component has, the shorter distance between bumps is caused. Due to this reason, when the electronic component is mounted via conductive adhesive agent having a high filler content rate (e.g., silver paste), the conductive adhesive agent is expanded between the bumps, which may cause a defective mounting between the electrodes (e.g., short circuiting). Also due to this reason, when the electronic component is mounted via nonconductive resin paste for example, limitation is caused on the reliability of the electric connection between the bump and the electrode.
The IC cards disclosed in Patent Publications 2 and 3 generally use a wiring board made of polyethylene terephthalate (PET) for the purpose of realizing a thinner thickness and reduced cost. However, since the PET-made wiring board is highly-flexible, the electronic component mounted above the wiring board causes the deflection and deformation of a part of the wiring board in the vicinity of a region at which a bump is pressed. Thus, the lower surface of the electronic component is close to the upper surface of the wiring board at positions in the vicinity of the edges of the electronic component and a position near the center between the bumps. When the electronic component is electrically-connected to the wiring board via anisotropic conductive resin for example in this case, conductive particles included in the anisotropic conductive resin are sandwiched between the electronic component and the wiring board at a part at which the electronic component is close to the wiring board. This consequently leads to electrical connection between the electronic component and the wiring board, resulting in a disadvantageous defective mounting of the electronic component for example.    [Patent Publication 1] Japanese translation of PCT publication H7-50726    [Patent Publication 2] Japanese Patent Unexamined Publication No. H11-175682    [Patent Publication 3] Japanese Patent Unexamined Publication No. 2005-111928